FOR THE SAKE OF CLARITY - Draeger
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FOR THE SAKE
OF CLARITY
Sewage doesn’t disappear that easily. It is purified in up to four stages
and then fed back into bodies of water. On the way
there, the finest analysis provides detailed information –
even about the sociodemographics of the population.
TEXT NILS SCHIFFHAUER PHOTOS PATRICK OHLIGSCHLÄGER
50 DRÄGER REVIEW 123 | 1 / 2021
RUBRIK
SCIENCE
THEMA
SEWAGE
ALL CLEAR
The purified sewage ends up
in one of these final clarifiers
been using chemical and microbiological
analysis to look beyond the supply and
disposal of water in order to gain insights
ou are what you eat, so they say. into people’s health and their consumption
And if you think a few hours further ahead, habits as well as the sociodemographic
something else can be added to this saying: structure of entire districts.
“... and what you leave behind you.” Urine To this end, the sewage is analyzed
and feces end up in the toilet, together using ever finer methods. More recently,
with toilet paper and other things that these methods have also helped to trace
don’t actually belong there. This mixture the SARS-CoV-2 virus, which caused the
is flushed away with water and ends up disease known as Covid-19 (“coronavi-
in the wastewater treatment plant via the rus”). Even before the WHO declared the
sewer system. Domestic and industrial infection a global pandemic on 11 March
wastewater mostly accumulates here. 2020, Professor Gertjan Medema, senior
For a number of years, scientists have microbiologist at the KWR Water Research
DRÄGER REVIEW 123 | 1 / 2021 51
SCIENCE
SEWAGE
VIRUSES IN THE SEWAGE INDICATE
INFECTIONS – INCLUDING COVID-19
Institute in the Dutch city of Nieuwegein, lutionary water researchers, and Aachen-
set to work with his team to prove the pres- based water researchers also showed that
ence of the specific residues of the caus- the presence of genetic SARS-CoV-2 mate-
al virus in the sewage: “If the number of rial in water treatment plants can also be
infected people increases, the viral pollu- proved with modern molecular methods.
tion in the sewage should also increase,” In all nine of the water treatment plants
says the microbiologist, explaining his tested in April 2020, analyses recorded
approach. “As such, corresponding mon- between three and 20 genocopies per
itoring of the sewage can ultimately serve milliliter of raw sewage, a concentra-
as an early-warning system for the out- tion level also measured in studies in
break (or recurrence) of Covid-19.” The the Netherlands and the USA. “If sensi-
team pursued a similar concept in 2009. tive enough, such analyses could serve as
an early-warning system for the authori- SKIMMING
SIGNS IN THE SEWAGE ties,” summarize the authors, “to enable Large screws keep the
aquatic plants at bay
Back then, the scientists were initially them to identify a local rise in cases in
in the clarifying basins
looking at the bird flu virus; then they the area around a water treatment plant that obviously feel
broadened their interest to include causes at an early stage.” at home here
of diseases such as polio, hepatitis A, and The project launched in spring
the norovirus, which causes vomiting 2020 under the aegis of Professor
and diarrhea. Health officials in the Georg Teutsch from the Helmholtz
Netherlands recorded the first Covid-19 Center for Environmental Research in
case on February 27, 2020, almost Leipzig (“Integral SARS-CoV-2 Sewage
three months after the outbreak of the Monitoring”) essentially wants to bring know, for example, whether the virus
epidemic in the Chinese city of Wuhan. clarity to the matter. “By continuously content in the stools changes in one and
The microbiologists started taking the monitoring the sewage, we want to the same person as the disease progresses
first samples just three weeks before shine a light on the unreported cases, or whether the rate differs from one
the country’s first case. Their aim: to provide a basis for taking decisions, person to the next.” These are questions
prove the presence of virus-specific and establish an early-warning system,” that make it just as difficult to translate
nucleic acids excreted in the stools of says the hydrogeologist. Members of the virus figures from the sewage into
those who were infected. The scientists the German Association for Water, the actual number of infected people as
traced the geographic progress of the Wastewater, and Waste (DWA) – including it does to establish a clear and reliable
infection over time by taking samples at Cologne’s municipal drainage works early-warning system. We currently have
specific locations agreed in conjunction (StEB) – are also involved in the project. around 20 people working on clarifying
with the health authorities. Professor Many problems have reportedly already this and other issues,” adds Prof. Teutsch.
Medema’s study in Amersfoort provided been solved, allowing the scientists to “That’s how science works!”
an indication of the potential suitability of identify evaluable signals in the highly
the concept as an early-warning system – diluted samples. The main question now FINDING THE SOURCE
subject to further research. Traces of the turns to what it all means. “An infected This is also the starting point for the
virus were found in the sewage before a individual,” explains Prof. Teutsch, “does supply and disposal of water as we know
single case had even been reported to the not excrete viruses on the very first it today. In 1854, the English physician
local health authority. day. And the amount of virus excreted John Snow bent over a map of London
In Germany, a consortium of Frank- differs for each infected person. Since and marked every cholera fatality with
furt-based virologists, ecotoxologists, evo- we measure the total content, we don’t a dash. Then he focused on the water
52 DRÄGER REVIEW 123 | 1 / 2021
“THERE IS A RISE IN THE
AMOUNT OF PAINKILLERS”
Dr. Andrea Poppe is the head of the
StEB’s sewage institute and is a member
of the board at the DWA* – it boasts
30 years’ experience in the sampling
and analysis of sewage.
Dr. Poppe, what is the purpose of performing this analysis?
With around 30 employees in our laboratory, we keep the population safe
by constantly monitoring the quality of the sewage and ensuring compliance
with legal regulations. Even if we are not allowed to conduct research
ourselves, because sewage charges directly serve our actual purpose,
we are, of course, focused on the future. Here we take part in scientific
studies like the Helmholtz Center’s coronavirus project.
What has changed over the years in terms of the
analysis we know today?
It now gives us much more precise and in-depth insights into the
substances contained in the sewage. Chemical analysis complements
biological methods where changes in the behavior of fish are examined,
for example.
What things in the sewage are especially problematic nowadays?
We are seeing a rise in the amount of pharmaceutical substances, such as
diclofenac, which is contained in painkillers. These are freely available to
buy and are clearly taken in large quantities prophylactically. They end up in
the water via excrement or as a result of not being disposed of properly.
Pain relief ointments also contain this substance, which then ends up in the
pumps and marked these with a dot. The
geographical link between the two was sewage when showering. X-ray contrast agents from doctor’s surgeries or
uncanny: The cholera epidemic of 1854 hospitals are equally problematic. And while toilet paper disintegrates in
was clearly caused by polluted water at the process, the same cannot be said of moist wipes, which are increasing
one of the pumps. This ran counter to being used. They block pipes and pumps and don’t belong in the toilet!
the theory popular at the time that this
How will the future of analysis develop?
disease was caused by miasmas. Yet this
It will certainly improve in terms of the quantities and substances it is able to
proved to be incorrect. It was a bacterium,
detect. The examination of sewage must keep pace with the changes in the
which an Italian doctor had discovered in
the same year. Even though it would be behavior of our customers. Microplastics, for example, are another challenge.
another 30 years before Robert Koch could * The German Association for Water, Wastewater, and Waste
prove the hypothesis of microorganisms,
John Snow’s discovery had consequences.
Particularly in the wake of the sewage
scandal of 1858, known as the Great Stink,
it led to a fundamental change in the
way water was supplied and disposed of
in London.
“In a certain way, we are still guided
by these insights and methods,” says Dr.
Andrea Poppe, head of the StEB’s sewage
DRÄGER REVIEW 123 | 1 / 2021 53
SCIENCE
SEWAGE
FROM SEWAGE TO CLEAR
WATER WITHIN A DAY
4.5
institute. One of Europe’s biggest and most
modern sewage treatment plants runs right
along the Rhine in the northeast of the city.
The StEB manages its large treatment
plant on a site covering 35 hectares. “It
is designed for the almost 1.6 million
so-called ‘population equivalents,’ which billion people worldwide live
we use to refer to the combined capacity for without functioning sewer systems
households and industry,” explains Martin
Grudzielanek. According to the head of
operations, this is where the purification
begins for up to 8.2 cubic meters of
water per second – from households and
industry. That is the equivalent to a total PRECISE CHECK
Sewage is constantly
of almost 80 million cubic meters per year.
80%
being sampled and
At the end of a process that takes just 24 analyzed at different
hours, during which the main task is to locations
absorb bacteria, around 220 million liters
of purified water flow into the Rhine from
eight final clarifiers up to 70 meters in of the world’s sewage is channeled
diameter. into the environment untreated
THEY COME UNANNOUNCED has generated itself. The StEB employees
For anyone who has stood at the strong- regularly check the contents of the sewage
smelling entry point and screening plant, system: “As such, I see places that not
which rakes out the coarsest matter before everybody gets to see that easily,” says
draining it of water (up to 6,000 tons Tobias Krebs. The chemistry technician
per year), the result is a minor miracle. “draws sewage samples,” as they say in the
That’s because it is not just fecal matter industry. “Including from companies or
that floats along the sewage system to An estimated the airport – wherever the sewage enters
55%
Stammheim. It is joined by toilet paper, the system – and of course unannounced.”
hygiene articles, food waste, dead rats, and Immediately afterwards while still in the
other things. Dräger fixed gas detectors car, the fresh suspension is homogenized
(Dräger PIR 3000/7000 and Polytron on a stirrer, divided into smaller vials,
3000) raise the alarm as soon as the gas is the figure by documented, and taken to the laboratory
content (such as hydrogen sulfide or which global water consumption in a cool bag for further examination –
methane) exceeds certain values. Sand is expected to rise by 2050 including a retained sample so that the
and suspended matter are filtered out in original sewage can be used at any time in
several stages. The sludge is treated further the event of a need to discuss any matters.
ILLUSTRATION: ISTOCK
until it harmlessly burns and can be used The Helmholtz researchers also advised
for generating energy. From 2030, the Dr. Andrea Poppe’s laboratory on the
city of Cologne plans to completely power best places to take samples for proving
its treatment plants using electricity it the presence of the virus. “We are also
54 DRÄGER REVIEW 123 | 1 / 2021
WHAT MAKES SOCIETY TICK?
A new trend involves using sewage to produce sociodemographic
data, which could even dispense with the need for a census or at
least complement it. How many residents in a city have a school
education? What percentage of them are divorced? Saer Samanipour
studies this and much more, not just with demographic statistics,
but by analyzing the wastewater. The doctor of chemistry and current
professor of molecular science used precise sensory analysis to test
the sewage of Australian cities for 40 substances from completely
different areas: drugs, antidepressants, sweeteners, or food. He used
the concentration of substances such as ethanol and amitriptyline
as markers for the consumption of alcohol and antidepressants.
He linked his findings with sociodemographic data gathered from a
census conducted at the same time. This allowed Samanipour to
develop a system of equivalents: a kind of yardstick that he could
place alongside the results of the chemical analysis in order to btain
data about the population’s social structure. From sewage systems
of unknown origin to him, he was able to make sometimes accurate
assertions about the social structure of the corresponding district.
FATBERGS CLOG SEWER PIPES
Time and again, sewer workers find large quantities of fat in the pipe
systems during inspections. Over time, they grow into huge lumps.
Such deposits in the sewer system occur when fats and oils are
disposed of via washbasins or toilets and end up in the sewage.
getting involved in this project by sending Objects such as wet wipes, diapers or cotton swabs that do not
samples,” says Dr. Poppe. belong in the toilet also cause these lumps. In 2017, one such
There is still no absolute certainty “fatberg” blocked London’s sewer system. It was 250 meters long
as to whether the coronavirus spreads and weighed more than 100 tons. Every year, Thames Water spends
through the sewage. A study published more than 13 million euros alone on clearing such deposits in the
in Nature in the summer found that sewer system of the British capital.
excreted viruses can remain active for
a few days in the wastewater of a sewer Here is a selection of things that do not belong in the toilet:
system and in aerosols. It concludes that •Leftover food; kitchen waste
a risk assessment should be carried out •Medication; tablets
and proposes disinfection with chlorine, •Moist wipes, moist toilet paper
treatment with ozone, or processes such as •Hygiene articles like panty liners, condoms, disposable
micro- and ultrafiltration with membrane diapers, or sticking plasters
filters. Other scientists dismiss this and •Toxic and aggressive substances like some toilet cleaners
point to the high dilution level, the short
•Deep-frying fat; cooking oils
lifespan, and the fact that just a fraction of
the virus material actually contains active
viruses in any case. Mankind’s sewage
disposal has always been put to good use in
the past. Analysis and evaluation continue
to write the story in unimagined ways.
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